With the voltage cycle increasing, the influence of
accumulated surface charges produced in the former halfcycle
on the location of discharge occurring in the latter halfcycle
was reduced. When the cycle of applied voltage
increased to 500 ms (as Figure 8), the coincidence rate of
hetero-discharge location before and after voltage zerocrossing
point became smaller. Besides, the coincidence
phenomenon of homo-discharge location during negative halfcycle
was observed (as Figure 8e), but the similar situation
during positive half-cycle did not appear. As voltage cycle
increased to 2000 ms (as Figure 9), the coincidence rate of
hetero-discharge location was further reduced, and the
coincidence phenomenon of homo-discharge location during
negative half-cycle appeared more frequently. There was still
no coincidence phenomenon of homo-discharge location
during positive half-cycle.